iosipodmpmediaquery

Retrieve list of songs ordered by last play time in iOS


I need to obtain a list of the N most recently played songs from an iOS device, in order.

The only way I can imagine doing it, at the moment, is by getting all the songs through an MPMediaQuery and manually sort them by lastPlayedDate.

This is a potentially expensive operation and I was wondering if there was a better approach.


Edit: After some tests, this is a very expensive operation. On a test library of 2500 songs, it took around 20 seconds to:

  1. Get all the songs.
  2. Assign a date to all songs that had never played (January 1 1970).
  3. Order them by date.
  4. Fetch the first N entries.

Any suggestion of improvements would be appreciated.


Edit 2: Solved now, but just for the record here's what I was doing.

I was sorting using a block as described here: https://stackoverflow.com/a/805589/112702. Simply changing the sorting method to what's in Bryan's answer improved my speed by nearly 20 times on an iPod Touch 3.


Solution

  • One way is to take the array of MPMediaItems you get from the MPMediaQuery and sort it by MPMediaItemPropertyLastPlayedDate using an NSSortDescriptor:

    NSTimeInterval start  = [[NSDate date] timeIntervalSince1970];
    
    MPMediaQuery *songsQuery = [MPMediaQuery songsQuery];
    NSArray *songsArray = [songsQuery items];
    
    NSSortDescriptor *sorter = [NSSortDescriptor sortDescriptorWithKey:MPMediaItemPropertyLastPlayedDate
                                                             ascending:NO];
    NSArray *sortedSongsArray = [songsArray sortedArrayUsingDescriptors:@[sorter]];
    
    NSTimeInterval finish = [[NSDate date] timeIntervalSince1970];
    NSLog(@"Execution took %f seconds.", finish - start);
    

    This sorts the new array by most recently played first. I tested this on a iPhone 4S using 2000 songs and it took .98 seconds.